Quaternary ammonium borohydrides and purification thereof



Jan. 4, 1966 R. w. BRAGDON ETAL. 3,227,755

QUATERNARY AMMONIUM BOROHYDRIDES AND PURIFICATION THEREOF Filed Jan. 28,1963 AYAVA A VV V7( VV vllYl/AVAVAVAVAVAVAVAVA AQYAYAVAVAVAVYAVAVAVAUnited States Patent O 3,227,755 QUATERNARY AMMONIUM BOROHYDRIDES ANDPURIFICATIGN THEREOF Robert W. Bragdon, Marblehead, and Edward A.Sullivan,

Beverly, Mass., assignors to Metal Hydrides Incorporated, Beverly,Mass., a corporation of Massachusetts Filed Jan. 28, 1963, Ser. No.254,395 20 Claims. (Cl. 260-567.6)

This invention relates to the purification of impure quaternary ammoniumborohydrides of the group having a total number ofvcarbon atoms from to15 inclusive in the organic substituents to the nitrogen atom, such astetraethylammonium borohydride, tetrapropylammonium borohydride, benzyltrimethyl ammonium borohydride, etc., containing certain impurities incertain amounts. The invention also related to the preparation of suchborohydrides in substantially pure form.

The United States patent to Banus, Gibb and Bragdon No. 2,738,369describes the preparation -of quaternary ammonium borohydrides byreacting a quaternary ammonium hydroxide with sodium -borohydride orpotassium borohydride in water, the reaction being illustrated by theequation:

Since both the quaternary ammonium borohydride 'and the alkali metalhydroxide are highly soluble in water, the quaternary ammoniumborohydride recovered usually contained a considerable amount of alkalimetal hydroxide as an impurity.

We have discovered that, subject to certain limitations, when certainquaternary ammonium borohydrides containing as an impurity one of thesalts sodium hydroxide, potassium hydroxide, potassium iluoride,potassium carbonate, potassium citrate, potassium tartirate, sodiumcarbonate, potassium sulfate or sodium sulfate, are extracted with anamount of water sulcient to dissolve substantially all the impurity butnot substantially more than the amount required to dissolve both theimpurity and the quaternary ammonium borohydride, a liquor is formedwhich, when permitted to settle, separates in two separate liquidlayers. The upper layer is essentially a saturated aqueous solution ofthe quaternary ammonium borohydride containing only a small 'amount ofthe impurity and the lower layer is an aqueous solution of the impuritycontaining only a small amount of quaternary ammonium borohydride. Theupper layer may be separated from the lower layer and substantially purequaternary ammonium borohydride recovered therefrom by crystallizationor by removing the water by evaporation. If too great an amount of wateris used the resulting liquor, when permitted to settle, will notseparate in two separate liquid layers.

If the amount of water used is not substantially more than that requiredto dissolve the impurity, the liquor formed is a solution ofsubstantially all the impurity and some of the quaternary ammoniumborohydride with a solid residue which is substantially pure quaternaryammonium borohydride. The solution, when permitted to settle, separatesin two separate layers. The upper layer is essentially a saturatedaqueous solution of the quater- 4nary ammonium borohydride and the lowerlayer is essentially an aqueous solution of the impurity containing asmall amount of the quaternary ammonium borohydride.

The impure quaternary ammonium borohydrides which may be treated by themethod of the invention are those having from 5 to 15 carbon atomsinclusive in the organic substituent to the nitrogen atom and in whichthe impurity is essentially one of the salts previously menice tioned.Illustrative examples of such quaternary ammonium borohydrides aretetraethylammonium borohydride, tetrapropylammonium borohydride, benzyltrimethylammonium borohydride, triethylmethylammonium borohydride,ethylpyridinium borohydride, and methylisoquinolinium borohydride. Themethod is not operative for treating an impure quaternary ammoniumborohydride containing less than a certain amount of the quaternaryammonium borohydride, the amount depending upon the solubility of thequaternary ammonium borohydride treated, the solubility of the impurity,and the temperature used for extraction as indicated more fullyhereinafter.

The invention willbe more clearly understood from the followingdescription in conjunction with the accompanying drawings, in which:

FIG. 1 shows two phase diagrams of the ternary systemswater-tetraethylammonium borohydride-sodium hydroxide illustrating areasrepresenting liquid compositions within the scope of the inventionobtained by extracting solid mixtures of tetraethylammonium borohydrideand sodium hydroxide at temperatures of 25 C. and 80 C.; and

FIG. 2 shows a phase diagram of the ternary'systemwater-tetrapropylammonium borohydride and potassium hydroxideillustrating areas containing liquor compositions within the scope ofthe invention obtained by extracting solid mixtures oftetrapropylammonium borohydride and potassium hydroxide at a tempertureof C.

Referring to FIG. l of the accompanying drawings, the apexes A, B, and Cof the large triangle represent percent tetraethylammonium borohydride,100 percent sodium hydroxide, and 100 percent water respectively, eachby weight. Any selected point P on the side AB of the trianglerepresents the amounts of tetraethylammonium borohydride and sodiumhydroxide in percent by weight in a solid impure tetraethylammoniumborohydride.

The full line and dotted line diagrams were established empirically byextracting impure borohydrides having varying amounts of sodiumhydroxide and tetraethylammonium borohydride with varying amounts ofwater at 25 C. and 80 C. respectively. The most important phase changes,viz. the rst appearance of two liquid phases and the reversion to asingle liquid phase on further dilution, are readily detected visuallyby the opalescence exhibited by systems containing two liquid phases,when agitated vigorously. Titration with water of a single known mixtureof quaternary ammonium borohydride and an alkali metal hydroxide can,then, determine three points on a ternary phase diagram such as thoseshown in FIG. l: l-the point at which all of the alkali metal hydroxidehas been dissolved (irst appearance of two liquid phases), 2-the pointat which all of the quaternary ammonium borohydri-de has been dissolved(absence of undissolved solids) and 3-the point at which only a singlehomogeneous phase is present (disappearance of two liquid phases). Fromthe Weights of the known mixtures and-of the quantities of waterrequired to reach these three points, the ternary compositions of thepoints can be calculated and plotted. Titration of several knownmixtures of divergent composition permits rapid outlining of the ternaryphase diagram. Referring to FIG. l, the area bounded by the fullstraight lines AF, AD, and the full curved line DEF` represents aqueousliquor compositions of tetraethylammonium borohydride and sodiumhydroxide obtained by extraction of solid mixtures of the borohydrideand hydroxide with wa'ter at a temperature of 25 C. These compositionsfall within the scope of the invention; that is, when the solution -ispermitted to settle at a temperature of 25 C. it separates in twoseparate layers, the upper layer being essentially a saturated aqueoussolution of the quaternary ammonium borohydride and a small amount ofthe alkali metal hydroxide and the lower layer being an aqueous solutionof the alkali metal hydroxide containing a small amount of borohydride.The remaining areas within the large triangle ABC represent liquidcompositions obtained by extraction at 25 C. which fall outside thescope of the invention; that is, when the solutions are permitted tosettle only a single liquid layer is formed. The line CI, drawn from theapex C through the point F, intersects the line AB at the point J. Thepoint I represents a solid impure tetraethylammonium borohydridecontaining about 5 percent by weight of the borohydride and indicatesthat, when extracting7 impure tetraethylammonium borohydride at 25 C.,the method of the invention is not operative if the solid impuretetraethylammonium borohydride contains less than about 5 percent byweight of borohydride.

The area within the full line triangle ADF represents aqueous liquorcompositions formed by extracting impure solid tetraethylammoniumborohydrides at 25 C. with suicient water to dissolve substantially allthe sodium hydroxide but not all the borohydride, the solid residuesbeing substantially pure tetraethylammonium borohydride. If the solutionis removed from the solid residue and permitted to settle, two separateliquid layers are formed, the upper layer being essentially a saturatedaqueous solution of tetraethylammonium borohydride and a small amount ofthe alkali metal hydroxide and the lower layer being an aqueous solutionof sodium hydroxide containing a small amount of borohydride.

The area bounded by the full straight line DF and the full curved lineDEF represents aqueous liquor compositions formed by extracting solidimpure tetraethylammonium borohydrides at 25 C. with suicient water todissolve all the borohydride as well as all the sodium hydr-oxide toform a liquor which, when permitted to settle, separates in two separatelayers, the upper layer being essentially a saturated aqueous solutionof the borohydride containing a small amount of sodium hydroxide and thelower layer being an aqueous solution of sodium hydroxide containing asmall amount of borohydride.

It will be apparent from the above that any impure tetraethylammoniumborohydride represented by the point P on the line AB in FIG. 1 may betreated by the method of the invention if a line drawn from the point Pto the apex C of the triangle ABC passes through the area bounded by thefull straight lines AF, AD, and the full curved line DEF. The line PC inFIG. l intersects the line AF at the point K and intersects the curvedline DEF at the point L. Any point on the portion KL of the line PCrepresents the amounts in percent by weight of tetraethylammoniumborohydride, sodium hydroxide and water in a liquor composition which,when permitted to settle at a temperature of 25 C., separates in twoseparate liquid layers, one of which is essentially a saturated aqueoussolution of tetraethylammonium borohydride which is from about 0.001 toabout 0.15 molar in sodium hydroxide, the other layer consistingessentially of an aqueous solution of sodium hydroxide.

If the extraction temperature is increased both the size and position ofthe area representing liquor compositions within the scope of theinvention is changed slightly. This is shown by comparing the dottedline diagram in FIG. l with the full line diagram. The area bounded bythe dotted straight lines AF', AD', and the dotted curved line DEFrepresents aqueous liquor compositions obtained by extracting solidmixtures of tetraethylammonium borohydride and sodium hydroxide withwater at 80 C. The line CI', drawn from the apex C through the point F',intersects the line AB at the point J'. The point J' represents a solidmixture of sodium hydroxide and tetraethylammonium borohydridecontaining about 18 percent by weight of the borohydride and indicatesthat, when extracting impure tetraethylammonium borohydride at C., themethod of the invention is not operative if the solid impure borohydridecontains less than about 18 percent by weight of borohydride.

Both the size and position of the areas in the diagram of the ternarysystems water-quate-mary ammonium borohydride-alkali .metal hydroxiderepresenting liquor compositions within the scope of the inventionchange with the water solubility -of the quaternary ammonium borohydrideand the alkali metal hydroxide impurity. In FIG. 2 of the accompanyingdrawings, the a-pexes A', B and C' of the large triangle represent 100percent tetrapropyl ammonium borohydride, percent potassium hydroxide,and 100 percent water respectively, each by weight. The area bounded bythe straight lines AF, AD, and the curved line D, E", and F" representsaqueous liquor `compositions of tetrapropylammonium borohydride andpotassium hydroxide within the scope of the invention obtained byextraction of solid mixtures of the borohydride and hydroxide with waterat 80 C. The line C'J", drawn from the apex C" through the point F",intersects the line AB' at the point J. The point I" represents a solidimpure tetrapropylammonum borohydride containing about 36 percent byweight of the borohydride and indicates that, when extracting impuretetrapropylammonium borohydride at 80 C., the method of the invention isnot operative if the solid impure tetrapropylammonium borohydridecontains less than about 36 percent by weight of borohydride.

It will be understood by those skilled in the art that a triangularphase diagram of any ternary system water, any salt selected from sodiumhydroxide, potassium hydroxide, potassium fluoride, potassium carbonate,potassium citrate, potassium tartrate, sodium carbonate, potassiumsulfate, and sodium sulfate, which for convenience we designated assplitting agents, and any quaternary ammonium borohydride selected fromthe group having a total number of carbon atoms from 5 to 15 in theorganic substituent to the nitrogen atom may be established empiricallyin the manner as described in connection with FIG. 1 having a closedarea similar to that shown in FIG. 1 representing the contents inpercent by weight -of water, the selected salt, and the selectedquaternary ammonium borohydride of liquor compositions which, whenpermitted to settle, separate in two irnmiscible liquid layers, theupper layer of which is essentially a saturated aqueous solution of theselected quaternary ammonium borohydride which is from about 0.001 toabout 0.15 molar in the selected salt and the other is essentially anaqueous solution of the selected salt.

When the selected salt in the above mentioned saturated aqueoussolutions of quaternary ammonium borohydride is either sodium hydroxideor potassium hydroxide, these aqueous solutions are unexpectedly morestable toward hydrolysis than those of other borohydrides undercomparable conditions. At 60 C. a three molar solution oftetraethylammonium borohydride which is 0.12 molar in sodium hydroxidehydrolyzes fourteen times slower than a three molar aqueous solution ofsodium borohydride which is 0.12 molar in sodium hydroxide. Thissignificantly higher stability makes such solutions attractive for longterm and/or high temperature applications, such as a storable andportable source of hydrogen for remote location fuel cells.

These aqueous solutions of quaternary ammonium borohydrides,particularly the aqueous solutions of tetraethylammonium borohydride,are very useful as nuclear shielding components, maintaining a highconcentration of hydrogen atoms per unit volume in a stable, nonammableaqueous system. Being liquid, such solutions uniformly lill complexstructural shapes without the danger of void formation. Furthermore, theshield solution can be forcibly circulated to provide heat exchange aswell. In these respects such solutions are unique in providing such acombination of properties. bility of the solutions is an added feature.

The present invention also provides a means for purifying quaternaryammonium borohydrides which contain salts other than those designated assplitting agents. For example, sodium metaborate can be separated from aquaternary ammonium borohydride by adding one of the splitting agentst-o the impure borohydride and then extracting the mixture with water.In such case, when the liquor is permitted `to settle, the metaboratewill be `found in the aqueous solution of the splitting agent.

The method of the invention may be embodied as a purification procedurein the preparation yof tetraethylammonium borohydride or otherquaternary ammonium borohydrides having a total number of carbon atomsfrom 5 to 15 in the organic substituents to the nitrogen atom. Thus,tetraethylammonium hydroxide may be reacted with sodium borohydride orpotassium borohydride in water as illustrated by Equation l above toform an aqueous solution of tetraethylammonium borohydride and thealkali metal hydroxide. The amount yof water in the solution then may beadjusted to produce a liquor having a composition such that, when it ispermitted to settle, it separates in two separate liquid layers, theupper layer of which is essentially a saturated aqueous solution oftetraethylammonium borohydride containing a small amount of the alkalimetal hydroxide. If desired, sodium borohydride may be used in the abovereaction in the form of a stabilized aqueous solution of sodiumborohydride and sodium hydroxide. Such a stabilized aqueous solution isdescribed in the patent to Robert W. Bragdon, No. 2,970,114, datedJanuary 31, 1961, and may contain from about 5 to 12.9 percent by weightof sodium borohydride and from about 35 to 46.9 percent by weight ofsodium hydroxide based upon the weight of the solution.

Similarly, the invention may be embodied as a puriiication procedure inthe preparation of any quaternary ammonium borohydrides having a totalnumber of carbon atoms from 5 to 15 in the organic substituent to thenitrogen atom. Thus, an aqueous solution of the quaternary ammoniumborohydride and a salt selected from sodium hydroxide, potassiumhyd-roxide, potassium fluoride, potassium carbonate, potassium citrate,potassium tartrate, sodium carbonate, potassium sulfate, or sodiumsulfate may be formed in which .the quaternary ammonium borohydride andat least a portion yof the selected salt is obtained by reacting eithersodium borohydride or potassium borohydride with an equimolar amount ofquaternary ammonium hydroxide, fluoride, carbonate, citrate, tartrate,or sulfate. The amount of water in the solution then may be adjusted toproduce a liquor having a composition such that, when permitted tosettle, it separates in two separate liquid layers, the upper layer ofwhich is essentially a saturated aqueous solution of the quaternaryammonium borohydride and a small amount of the selected salt and thelower layer is essentially an aqueous solution of the selected salt.

The invention is illustrated further by the following specific examples.

The sta- Exam ple 1 Extraction of 31.2 grams of 67.6 percent puretetraethylammonium borohydride containing sodium hydroxide as animpurity with 25 ml. of water at 60 C. resulted in complete dissolutionof the solids. The resulting liquor, when permitted to settle, separatedin two immiscible layers. Crystallization occurred when the upper layerwas cooled. Filtration and drying of the crystals resulted in recoveryof 6.7 grams of 99.3 percent pure tetraethylammonium borohydride. Theyield can be improved by recycling the upper layer to subsequentpurication.

Example 2 40 grams of 52.9 percent pure tetraethylammonium borohydridecontaining potassium hydroxide as an impurity was extracted with 25 ml.of water at 60 C. and the resulting liquor was treated as abovedescribed to recover 2.7 grams of 95.7 percent pure tetraethylammoniumborohydride.

Example 59 grams of 41.0 percent pure benzyl trimethylammoniumborohydride containing sodium hydroxide as an impurity were extractedwith 58 ml. of water at 60 C. Thirteen grams of 88.2 percent pure benzyltrimethylammonium borohydride was recovered from the resulting liquorwhen processed as described in Example 1.

Example 4 44 grams of 38.9 percent pure tetrapropylammonium borohydridecontaining sodium hydroxide as an impurity were extracted with 32 ml. ofwater at 60 C., resulting in complete dissolution of the solids. Theresulting liquor, when permitted to settle, separated into twoimmiscible layers. Separation and vacuum drying of the top layerresulted in the recovery of 12.4 grams of 88.9 percent puretetrapropylammonium borohydride.

Example 5 Addition of 17.7 grams of 99.5 percent pure sodium borohydride(0.467 mole) to 110 grams of an aqueous solution containing 44 percentby weight of tetraethylammonium hydroxide resulted in completedissolution of the sodium borohydride and the formation of twoimmiscible layers at room temperature. When the Itop layer was separatedand taken to dryness under vacuum, 49 grams of 97.1 percent puretetraethylammonium borohydride were recovered.

Example 6 Forty pounds of 98.5% pure sodium borohydride (1.04 lb.mole)were .added to 366 pounds of 40.25% aqueous tetraethylammonium hydroxide(1.00 lb.mole) in pilot plant equipment. The mixture was stirred andallowed to settle, whereby two immiscible layers were formed at roomtemperature, The top layer was separated physically and dried undervacuum at C. A total of 141.5 lbs. of 99.0% pure tetraethylammoniumborohydride were recovered, representing a 97.5% yield.

We claim:

1. In a method for purifying a quaternary ammonium borohydridecontaining as an impurity a salt selected from the group consisting ofsodium hydroxide, potassium hydroxide, potassium uoride, potassiumcarbonate, potassium citrate, potassium tartrate, sodium carbonate,potassium sulfate and sodium sulfate, said borohydride being selectedfrom the group consisting of tetraethylammonium borohydride,tetrapropylammonium borohydride, benzyltrimethylammonium fborohydride,triethylmetihylamrnonium borohydride, ethylpyridinium borohydride, andmethylisoquinolinium borohydride, said impure quaternary ammoniumborohydride containing substantial amounts of said impurity andquaternary ammonium borohydride, the step comprising extracting thesolid impure quaternary ammonium borohydride with -an amount of Water toform two immiscible layers, one of which is essentially an aqueoussolution of the quaternary ammonium borohydride and the other isessentially `an aqueous solution of said salt.

2. The method as claimed by claim 1 wherein the selected quaternaryammonium borohydride is tatraethylammonium borohydride.

3. The method as `claimed by claim 1 wherein the selected quaternaryammonium borohydride is tetrapropylammonium borohydride.

4. The method as claimed by claim 1 wherein the selected quaternaryammonium borohydride is benzyltrimethylammonium borohydride.

5. In a method for preparing a quaternary ammonium borohydride selectedfrom the group consisting of tetraethylammonium borohydride,tetrapropylammonium borohydride, benzyltrimethylammonium borohydride,triethylmethylammonium borohydride, ethylpyridinium borohydride, andmethylisoquinolinium borohydride, the steps which comprise forming anaqueous solution of sodium hydroxide and the quaternary ammoniumborohydride in which the quaternary ammonium borohydride and at least aportion of the sodium hydroxide is obtained by treacting sodiumborohydride with substantially an equimolar amount of a quaternaryammonium hydroxide, adjusting the amount of Water in said solution suchthat two immiscible layers are formed, one of which is essentially anaqueous solution of the quaternary ammonium borohydride and the other isessentially an aqueous solution of sodium hydroxide.

6. The method as claimed by claim wherein the selected quaternaryammonium borohydride is tetraethylammonium borohydride.

7. The method as claimed by claim 5 wherein the selected quaternaryammonium borohydride is tetrapropylammonium borohydride.

8. The method as claimed by claim 5 wherein the selected quaternaryammonium borohydride is benbyltrimethylammonium borohydride.

9. In a method for preparing a quaternary ammonium borohydride selectedfrom the group consisting of tetraethylammonium borohydride,tetrapropylammonium borohydride, benzyltrimethylammonium borohydride,ethylpyridinium borohydride, and methylisoquinolinium borohydride, thesteps which comprise forming an aqueous solution of the quaternaryammonium borohydride and a salt selected from the group consisting7 ofsodium hydroxide, potassium hydroxide, potassium uoride, potassiumcarbonaite, potassium sulfate, potassium citrate, potassium tartrate,sodium carbonate, and sodium sulfate in which at least a portion of saidsalt is obtained by reacting an alkali metal borohydride selected fromthe group consisting of sodium borohydride and potassium borohydridewith a substantially equimolar amount of a quaternary ammonium salt,adjusting the amount of water in said solution such that two immisciblelayers are formed, one of which is essentially an aqueous solution ofthe quaternary ammonium borohydride and the other is essentially anaqueous solution of said salt.

10. The method as claimed by claim 9 wherein the selected quaternaryammonium borohydride is tetraethylammonium borohydride.

11. The method as claimed by claim 9 wherein the selected quaternaryammonium borohydride is tetrapropylammonium borohydride.

12. The method as claimed by claim 9 wherein the selected quaternaryammonium borohydride is benzyltrimethylammonium borohydride.

l13. The method as claimed by claim 9 wherein said 8 selected alkalimetal borohydride is sodium borohydride and said selected salt sodiumhydroxide.

14. The method as claimed by claim 9 wherein said selected alkali metalborohydride is sodium borohydride and said selected salt is sodiumcarbonate.

15. The method as claimed by claim 9 wherein said selected alkali metalborohydride is sodium borohydride and said selected salt is sodiumsulfate.

16. In a method for purifying an impure tetraethylammonium borohydridecontaining sodium hydroxide as an impurity in an amount not exceedingabout percent by weight which comprises extracting the impureborohydride with an amount of water at a temperature of about 25 C. toform a liquor in which the amounts of tetraethylammonium borohydride,sodium hydroxide and water in percent by weight based upon the weight ofthe liquor are represented by a point within the area AFEDA shown inFIGURE l, and permitting the solution portion of said liquor to settleat a temperature of about 25 C. thereby forming two separate immisciblelayers, one of which consists essentially of an aqueous solution oftetraethylammonium borohydride and the other consists essentially of anaqueous solution of sodium hydroxide.

17. As a composition of matter an aqueous solution consisting of aquaternary ammonium borohydride selected from the group consisting oftetraethylammonium borohydride, tetrapropylammonium borohydride,benzyltrimethylammonium borohydride, triethylmethylammonium borohydride,ethylpyridinium borohydride, and methylisoquinolinium borohydride and asalt selected from the group consisting of sodium hydroxide, potassiumhydroxide, potassium uoride, potassium carbonate, potassium citrate,potassium tartrate, sodium carbonate, potassium sulfate and sodiumsulfate and having two immiscible layers, one of which is essentially anaqueous solution of the quaternary ammonium borohydride and the other isessentially an aqueous solution of said salt.

18. A composition of matter as claimed by claim 16 wherein the selectedquaternary ammonium borohydride is tetraethylammonium borohydride.

19. A composition of matter as claimed by claim 16 wherein the selectedquaternary ammonium borohydride is benzyltrimethylammonium borohydride.

20. A composition of matter as claimed by claim 16 wherein the selectedquaternary ammonium borohydride is tetrapropylammonium borohydride.

OTHER REFERENCES Bonus et al.: I.A.C.S., Vol. 74, pp. 2346e2348 (1955).

CHARLES B. PARKER, Primary Examiner.

FLOYD D. HIGEL, Assistant Examiner.

1. IN A METHOD FOR PURIFYING A QUATERNARY AMMONIUM BOROHYDRIDECONTAINING AS AN IMPURITY A SALT SELECTED FROM THE GROUP CONSISTING OFSODIUM HYDROXIDE, POTASSIUM HYDROXIDE, POTASSIUM FLUORIDE, POTASSIUMCARBONATE, POTASSIUM CITRATE, POTASSIUM TARTRATE, SODIUM CARBONATE,POTASSIUM SULFATE AND SODIUM SULFATE, SAID BOROHYDRIDE BEING SELECTEDFROM THE GROUP CONSISTING OF TETRAETHYLAMMONIUM BOROHYDRIDE,TETRAPROPYLAMMONIUM BOROHYDRIDE, BENZYLTRIMETHYLAMMONIUM BOROHYDRIDE,TRIETHYLMETHYLAMMONIUM BOROHYDRIDE, ETHYLPYRIDINIUM BOROHYDRIDE, ANDMETHYLISOQUINOLINIUM BOROHYDRIDE, SAID IMPURE QUATERNARY AMMONIUMBOROHYDRIDE CONTAINING SUBSTANTIAL AMOUNTS OF SAID IMPURITY ANDQUATERNARY AMMONIUM BOROHYDRIDE, THE STEP COMPRISING EXTRACTING THESOLID IMPURE QUATERNARY AMMONIUM BOROHYDRIDE WITH AN AMOUNT OF WATER TOFORM TWO IMMISCIBLE LAYERS, ONE OF WHICH IS ESSENTIALLY AN AQUEOUSSOLUTION OF THE QUATERNARY AMMONIUM BOROHYDRIDE AND THE OTHER ISESSENTIALLY AN AQUEOUS SOLUTION OF SAID SALT.
 17. AS A COMPOSITION OFMATTER AN AQUEOUS SOLUTION CONSISTING OF A QUATERNARY AMMONIUMBOROHYDRIDE SELECTED FROM THE GROUP CONSISTING OF TETRAETHYLAMMONIUMBOROHYDRIDE, TETRAPROPYLAMMONIUM BOROHYDRIDE, BENZYLTRIMETHYLAMMONIUMBOROHYDRIDE, TRIETHYLMETHYLAMMONIUM BOROHYDRIDE, ETHYLPYRIDINIUMBOROHYDRIDE, AND METHYLISOQUINOLINIUM BOROHYDRIDE AND A SALT SELECTEDFROM THE GROUP CONSISTING OF SODIUM HYDROXIDE, POTASSIUM HYDROXIDE,POTASSIUM FLUORIDE, POTASSIUM CARBONATE, POTASSIUM CITRATE, POTASSIUMTARATRATE, SODIUM CARBONATE, POTASSIUM SULFATE AND SODIUM SULFATE ANDHAVING TWO IMMISCIBLE LAYERS, ONE OF WHICH IS ESSENTIALLY AN AQUEOUSSOLUTION OF THE QUATERNARY AMMONIUM BOROHYDRIDE AND THE OTHER ISESSENTIALLY IN AQUEOUS SOLUTION OF SAID SALT.